1. Field of the Invention
The present invention relates to a magnetooptical disc recording apparatus having an optical head and a magnetic head, and more particularly to a magnetooptical disc recording apparatus having a means for lessening the effect of magnetic and electric fields on a magnetic head.
2. Description of the Prior Art
Heretofore, magnetooptical disc recording apparatus employ a magnetooptical disc as a recording medium for magnetooptically recording information thereon. The magnetooptical disc has a magnetic film which is easily magnetizable in a direction perpendicular to the surface of the magnetic film, the magnetic film having a large coercive force. A small region on the magnetic film is heated by a laser beam or the like, and a magnetic field is applied to reverse the direction of magnetization in the heated region, thus producing a recorded bit on the magnetic film. The information represented by the recorded bit can be reproduced using the magnetooptical effect. The magnetooptical disc recording apparatus have an optical head and a magnetic head that are positioned one on each side of the magnetooptical disc in confronting relationship to each other. The optical head and the magnetic head are structurally coupled to each other by a link mechanism. When the magnetooptical disc rotates or any location thereon is to be accessed by the optical and magnetic heads, the optical and magnetic heads are movable in unison with each other to record desired information on and reproduce recorded information from the magnetooptical disc.
The magnetic head comprises an assembly of a coil, a core with the coil mounted thereon, and a holder which positions the coil and the core in place. It is necessary to provide against electromagnetic inductions, i.e., effects which the magnetic field generated by the magnetic head has on other components and devices, and effects which the magnetic fields generated by other components and devices have on the magnetic head.
FIG. 1 of the accompanying drawings shows one conventional measure against electromagnetic inductions which comprises an electromagnetic shield box 30 that houses a magnetooptical disc recording apparatus for thereby electromagnetically shielding the entire apparatus. As shown in FIG. 1, the magnetooptical disc recording apparatus includes a disc cartridge assembly 1 having a cartridge 2 composed of a pair of upper and lower cartridge members. The lower cartridge member has a central opening 2a defined therein, and the upper and lower cartridge members have respective windows 2b defined respectively therein near one side edge thereof. The cartridge 2 accommodates therein a magnetooptical disc 3 which is partly exposed through the windows 2b that can selectively be opened and closed by a shutter 4.
A spindle motor 5 has a rotatable shaft connected coaxially to a turntable 6 rotatably disposed in the central opening 2a in the lower cartridge member. The magnetooptical disc 3 is supported on the turntable 6, so that it can be rotated in the cartridge 2 when the spindle motor 5 is energized. The magnetooptical disc recording apparatus also includes an optical head 7 and a magnetic head 8 that vertically confront each other and are movably positioned in the respective windows 2b in the upper and lower cartridge members. The optical and magnetic heads 7, 8 are supported by a link mechanism 9, one on each side of the cartridge 2, i.e., one on each side of the magnetooptical disc 3 housed therein. The link mechanism 9 is reciprocally movable radially with respect to the magnetooptical disc 3 by a feed mechanism 10 which comprises a motor and a feed shaft coupled thereto.
When the magnetooptical disc 3 is rotated or is to be accessed by the optical and magnetic heads 7, 8, the optical and magnetic heads 7, 8 are moved in unison with each other radially with respect to the magnetooptical disc 3 by the feed mechanism 10 through the link mechanism 9 to record desired information on and reproduce recorded information from the magnetooptical disc 3.
Since the magnetooptical disc recording apparatus is electromagnetically shielded in its entirety by the electromagnetic shield box 30 which houses the magnetooptical disc recording apparatus, the overall assembly is relatively large in size and weight, and costly because of the additional magnetic shield box 30. Therefore, the conventional electromagnetic shield structure has been contrary to efforts to meet requirements for cutdowns in the size, weight, and cost of the overall assembly.